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1. The TESS-Keck Survey. XVII. Precise Mass Measurements in a Young, High-multiplicity Transiting Planet System Using Radial Velocities and Transit Timing Variations

   https://doi.org/10.3847/1538-3881/ad1330  

   Beard, Corey ; Robertson, Paul ; Dai, Fei ; Holcomb, Rae ; Lubin, Jack ; Akana Murphy, Joseph M. ; Batalha, Natalie M. ; Blunt, Sarah ; Crossfield, Ian ; Dressing, Courtney ; et al ( January 2024 , The Astronomical Journal)

   We present a radial velocity (RV) analysis of TOI-1136, a bright Transiting Exoplanet Survey Satellite (TESS) system with six confirmed transiting planets, and a seventh single-transiting planet candidate. All planets in the system are amenable to transmission spectroscopy, making TOI-1136 one of the best targets for intra-system comparison of exoplanet atmospheres. TOI-1136 is young (∼700 Myr), and the system exhibits transit timing variations (TTVs). The youth of the system contributes to high stellar variability on the order of 50 m s⁻¹, much larger than the likely RV amplitude of any of the transiting exoplanets. Utilizing 359 High Resolution Echelle Spectrometer and Automated Planet Finder RVs collected as part of the TESS-Keck Survey, and 51 High-Accuracy Radial velocity Planetary Searcher North RVs, we experiment with a joint TTV-RV fit. With seven possible transiting planets, TTVs, more than 400 RVs, and a stellar activity model, we posit that we may be presenting the most complex mass recovery of an exoplanet system in the literature to date. By combining TTVs and RVs, we minimized Gaussian process overfitting and retrieved new masses for this system: (m_b−g=${3.50}_{-0.7}^{+0.8}$,${6.32}_{-1.3}^{+1.1}$,${8.35}_{-1.6}^{+1.8}$,${6.07}_{-1.01}^{+1.09}$,${9.7}_{-3.7}^{+3.9}$,${5.6}_{-3.2}^{+4.1}$M_⊕). We are unable to significantly detect the mass of the seventh planet candidate in the RVs, but we are able to loosely constrain a possible orbital period near 80 days. Future TESS observations might confirm the existence of a seventh planet in the system, better constrain the masses and orbital properties of the known exoplanets, and generally shine light on this scientifically interesting system.

    

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2. The TESS-Keck Survey. XVIII. A Sub-Neptune and Spurious Long-period Signal in the TOI-1751 System

   https://doi.org/10.3847/1538-3881/ad29ee  

   Desai, Anmol ; Turtelboom, Emma V. ; Harada, Caleb K. ; Dressing, Courtney D. ; Rice, David R. ; Murphy, Joseph M. Akana ; Brinkman, Casey L. ; Chontos, Ashley ; Crossfield, Ian J. M. ; Dai, Fei ; et al ( April 2024 , The Astronomical Journal)

   We present and confirm TOI-1751 b, a transiting sub-Neptune orbiting a slightly evolved, solar-type, metal-poor star (T_eff= 5996 ± 110 K,$\log (g)=4.2\pm 0.1$,V= 9.3 mag, [Fe/H] = −0.40 ± 0.06 dex) every 37.47 days. We use TESS photometry to measure a planet radius of${2.77}_{-0.07}^{+0.15}{R}_{\oplus }$. We also use both Keck/HIRES and APF/Levy radial velocities (RV) to derive a planet mass of${14.5}_{-3.14}^{+3.15}{M}_{\oplus }$, and thus a planet density of 3.6 ± 0.9 g cm⁻³. There is also a long-period (∼400 days) signal that is observed in only the Keck/HIRES data. We conclude that this long-period signal is not planetary in nature and is likely due to the window function of the Keck/HIRES observations. This highlights the role of complementary observations from multiple observatories to identify and exclude aliases in RV data. Finally, we investigate the potential compositions of this planet, including rocky and water-rich solutions, as well as theoretical irradiated ocean models. TOI-1751 b is a warm sub-Neptune with an equilibrium temperature of ∼820 K. As TOI-1751 is a metal-poor star, TOI-1751 b may have formed in a water-enriched formation environment. We thus favor a volatile-rich interior composition for this planet.

    

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3. GJ 3929: High-precision Photometric and Doppler Characterization of an Exo-Venus and Its Hot, Mini-Neptune-mass Companion

   https://doi.org/10.3847/1538-4357/ac8480  

   Beard, Corey ; Robertson, Paul ; Kanodia, Shubham ; Lubin, Jack ; Cañas, Caleb I. ; Gupta, Arvind F. ; Holcomb, Rae ; Jones, Sinclaire ; Libby-Roberts, Jessica E. ; Lin, Andrea S. J. ; et al ( August 2022 , The Astrophysical Journal)

   We detail the follow-up and characterization of a transiting exo-Venus identified by TESS, GJ 3929b (TOI-2013b), and its nontransiting companion planet, GJ 3929c (TOI-2013c). GJ 3929b is an Earth-sized exoplanet in its star’s Venus zone (P_b= 2.616272 ± 0.000005 days; S_b=${17.3}_{-0.7}^{+0.8}$S_⊕) orbiting a nearby M dwarf. GJ 3929c is most likely a nontransiting sub-Neptune. Using the new, ultraprecise NEID spectrometer on the WIYN 3.5 m Telescope at Kitt Peak National Observatory, we are able to modify the mass constraints of planet b reported in previous works and consequently improve the significance of the mass measurement to almost 4σconfidence (M_b= 1.75 ± 0.45M_⊕). We further adjust the orbital period of planet c from its alias at 14.30 ± 0.03 days to the likely true period of 15.04 ± 0.03 days, and we adjust its minimum mass to$m\sin i$= 5.71 ± 0.92M_⊕. Using the diffuser-assisted ARCTIC imager on the ARC 3.5 m telescope at Apache Point Observatory, in addition to publicly available TESS and LCOGT photometry, we are able to constrain the radius of planet b toR_p= 1.09 ± 0.04R_⊕. GJ 3929b is a top candidate for transmission spectroscopy in its size regime (TSM = 14 ± 4), and future atmospheric studies of GJ 3929b stand to shed light on the nature of small planets orbiting M dwarfs.

    

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4. TESS-Keck Survey. XIV. Two Giant Exoplanets from the Distant Giants Survey

   https://doi.org/10.3847/1538-3881/aca6ef  

   Van Zandt, Judah ; Petigura, Erik A. ; MacDougall, Mason ; Gilbert, Gregory J. ; Lubin, Jack ; Barclay, Thomas ; Batalha, Natalie M. ; Crossfield, Ian J. M. ; Dressing, Courtney ; Fulton, Benjamin ; et al ( January 2023 , The Astronomical Journal)

   We present the Distant Giants Survey, a three-year radial velocity campaign to measure P(DG∣CS), the conditional occurrence of distant giant planets (DG;M_p∼ 0.3–13M_J,P> 1 yr) in systems hosting a close-in small planet (CS;R_p< 10R_⊕). For the past two years, we have monitored 47 Sun-like stars hosting small transiting planets detected by TESS. We present the selection criteria used to assemble our sample and report the discovery of two distant giant planets, TOI-1669 b and TOI-1694 c. For TOI-1669 b we find that$M\sin i=0.573\pm 0.074M_{\mathrm{J}}$,P= 502 ± 16 days, ande< 0.27, while for TOI-1694 c,$M\sin i=1.05\pm 0.05M_{\mathrm{J}}$,P= 389.2 ± 3.9 days, ande= 0.18 ± 0.05. We also confirmed the 3.8 days transiting planet TOI-1694 b by measuring a true mass ofM= 26.1 ± 2.2M_⊕. At the end of the Distant Giants Survey, we will incorporate TOI-1669 b and TOI-1694 c into our calculation of P(DG∣CS), a crucial statistic for understanding the relationship between outer giants and small inner companions.

    

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5. TOI-1670 b and c: An Inner Sub-Neptune with an Outer Warm Jupiter Unlikely to Have Originated from High-eccentricity Migration

   https://doi.org/10.3847/1538-3881/ac5c4f  

   Tran, Quang H. ; Bowler, Brendan P. ; Endl, Michael ; Cochran, William D. ; MacQueen, Phillip J. ; Gandolfi, Davide ; Persson, Carina M. ; Fridlund, Malcolm ; Palle, Enric ; Nowak, Grzegorz ; et al ( April 2022 , The Astronomical Journal)

   We report the discovery of two transiting planets around the bright (V= 9.9 mag) main-sequence F7 star TOI-1670 by the Transiting Exoplanet Survey Satellite. TOI-1670 b is a sub-Neptune ($R_{\mathrm{b}}={2.06}_{-0.15}^{+0.19}$R_⊕) on a 10.9 day orbit, and TOI-1670 c is a warm Jupiter ($R_{\mathrm{c}}={0.987}_{-0.025}^{+0.025}$R_Jup) on a 40.7 day orbit. Using radial velocity observations gathered with the Tull Coudé Spectrograph on the Harlan J. Smith telescope and HARPS-N on the Telescopio Nazionale Galileo, we find a planet mass of$M_{\mathrm{c}}={0.63}_{-0.08}^{+0.09}$M_Jupfor the outer warm Jupiter, implying a mean density of${\rho }_c={0.81}_{-0.11}^{+0.13}$g cm⁻³. The inner sub-Neptune is undetected in our radial velocity data (M_b< 0.13M_Jupat the 99% confidence level). Multiplanet systems like TOI-1670 hosting an outer warm Jupiter on a nearly circular orbit ($e_{\mathrm{c}}={0.09}_{-0.04}^{+0.05}$) and one or more inner coplanar planets are more consistent with “gentle” formation mechanisms such as disk migration or in situ formation rather than high-eccentricity migration. Of the 11 known systems with a warm Jupiter and a smaller inner companion, eight (73%) are near a low-order mean-motion resonance, which can be a signature of migration. TOI-1670 joins two other systems (27% of this subsample) with period commensurabilities greater than 3, a common feature of in situ formation or halted inward migration. TOI-1670 and the handful of similar systems support a diversity of formation pathways for warm Jupiters.

    

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